Malaria remains a devastating health problem in endemic malaria regions of Brazil and Colombia with over 600,000 annual cases reported. Our ecological and evolutionary evidence indicate that the underlying biological complexity among anopheline vectors plays a significant role in continued malaria transmission in the Neotropics. We have convincing data from peri-urban settings that Anopheles marajoara of the Albitarsis Complex increases in importance and even replaces the primary malaria vector An. darlingi in NE Amazonian Brazil, although An. darlingi continues to be important in frontier and riverine settlements. We have described a new malaria vector, Anopheles albitarsis E, from peri-urban savanna in northern Amazonian Brazil. We hypothesize that An. marajoara is restricted to moist forest and An. albitarsis E is restricted to savanna. We recently detected two new species, An. albitarsis F, from NE Colombia, and An. albitarsis G, from Central Amazonian Brazil. Both are in endemic malaria areas, and both are putative malaria vectors. Neither has been characterized. Effective biologically-informed control of Neotropical malaria vectors requires contributions from three areas: fast and accurate vector identification, population genetics and ecology. We hypothesize that distinctive patterns of malaria transmission (frontier vs. peri-urban) are often related to anthropogenic habitat alterations that differentially favor various vector species that have distinct ecological requirements. We propose to evaluate the taxonomic status of several newly detected species with crossing experiments and cytology, and for rapid field identification, we will improve our molecular markers to more easily distinguish among all species in the Albitarsis Complex. We will test our hypothesis of habitat segregation between An. marajoara and An. darlingi by breeding site characterization. We will assess the importance of An. marajoara, An. albitarsis F, and An. darlingi in peri-urban endemic malaria localities in Colombia through evaluation of species abundance, biting time, infection and host selection in heterogeneous habitat sites. In Brazil, we determined that population structure and history differ substantially for An. darlingi and An. marajoara. We will use data from transects to evaluate the roles of climatic variables and highways vs. rivers in distribution, population structure and gene flow in each species. Project Narrative: Malaria is one of the most important public health problems in Brazil and Colombia. A better understanding of the ecology and evolution of the mosquito vectors, the objects of this study, will help to reduce human-mosquito contact and malaria, which disproportionately affects the poorest, mostly rural communities globally.